1. Field of the Invention
The present invention relates to an insulated packaging material which comprises a film of first and second face material layers laminated to a thermal insulating layer and a microwave susceptible coating applied to the second face material layer so that the second layer is preferentially heated by microwave radiation. The first face material layer can be coated with a coating material so that it is printable to form a combination microwave susceptible insulated label and packaging material.
2. Description of Related Art
Insulated enclosures for containers are known, such as that disclosed in U.S. Pat. No. 4,871,597. This enclosure includes a first, or inner-most fabric layer, a second inner-most insulating layer which includes a polymeric foam, a third inner-most metallized polymer film reflective layer, and an outer-most fabric mesh layer. However, the use of four different layers, although providing good insulation for the container, can be cumbersome, which limits the flexibility of the packaging material.
Also known in the film art is a thin electrical tape which comprises a polyester web-reinforced polyester film, as disclosed in 3M Utilities and Telecommunications OEM. However, this tape, which at its thickest is 0.0075 inch (0.0190 cm.), is not suitable for use as an insulated packaging material.
Composite materials for use as microwave susceptors are also known. U.S. Pat. No. 5,021,293 shows a polyethylene terephthalate film coated with flakes of electrically conductive metal or metal alloy. U.S. Pat. No. 4,892,782 shows drapable liquid permeable woven or nonwoven fibrous dielectric substrates that are coated with susceptor materials which can be wrapped around food items for microwave heating. These patents do not disclose both microwave susceptible and insulated packaging materials, nor such packaging materials that may also be printed as labels.
Thus, there exists a need to design an insulated packaging material which is inexpensive to manufacture. Such an insulator would be thick enough to provide adequate insulation, but thin enough to be flexible. Ideally, such packaging material also would be printable to form a label.